Analog-to-digital converter with low power track-and-hold mode

Abstract

A method for converting analog data to digital data includes operating an analog-to-digital data converter in a tracking mode to sample an input signal and in a convert mode to convert the sampled input signal after sampling to a digital signal. The analog-to-digital data converter is controlled with a controller to operate in different modes of operation by providing at least one step wherein the tracking mode of operation is controlled to initiate at a predetermined time to begin the sampling operation.

1. A method for converting analog data to digital data, comprising the steps of:
 operating an analog-to-digital data converter in a tracking mode to sample an input signal and in a convert mode to convert the sampled input signal after sampling to a digital signal; and 
 controlling with a controller the operation of the analog-to-digital data converter to operate in different track modes of operation by providing at least one step wherein the tracking mode of operation is controlled to initiate at a predetermined time to begin the sampling operation after a non tracking period wherein no sampling occurs and no conversion operation occurs. 
 
   
   
     2. The method of  claim 1 , wherein the analog-to digital data converter operates under the control of a data converter clock, wherein the convert mode operates over a predetermined number of clock cycles of the data converter clock. 
   
   
     3. The method of  claim 2 , wherein the step of controlling comprises controlling the operation of the analog-to-digital data converter in the tracking mode to sample the input signal for a predetermined amount of time prior to the beginning of the convert mode of operation. 
   
   
     4. The method of  claim 3 , wherein the predetermined amount of time comprises a predetermined number of clock cycles of the data converter clock. 
   
   
     5. The method of  claim 4 , wherein the beginning of the tracking mode is controlled to operate in a plurality of different initiation modes controlled by external stimuli. 
   
   
     6. The method of  claim 5 , wherein one of the stimuli comprises the step of initiating the tracking mode in response to the setting of a data bit in a register which, when read in the set state, indicates the start of the tracking mode. 
   
   
     7. The method of  claim 6 , wherein the convert mode of operation is initiated at the end of the predetermined time such that setting of the data bit causes operation in the convert mode. 
   
   
     8. The method of  claim 5 , wherein one of the stimuli comprises the step of initiating the tracking mode in response to an elapse of time determined by a timer, the elapse of which indicates the start of the tracking mode. 
   
   
     9. The method of  claim 8 , wherein the convert mode of operation is initiated at the end of the predetermined time such that the elapse of time is the causative effect to initiate the convert mode of operation. 
   
   
     10. The method of  claim 1 , wherein, in one of the track modes operation, the beginning of the convert mode is controlled to operate in response to receipt an external convert start signal being in a first of two states and the tracking mode is controlled to operate when the convert start signal is in the other of the two states. 
   
   
     11. The method of  claim 1 , wherein the convert mode operates in accordance with a SAR data conversion algorithm. 
   
   
     12. A method for converting analog data to digital data, comprising the steps of:
 sampling an input signal onto an input of an analog-to-digital data converter in a tracking mode; 
 converting in a convert mode with the analog-to-digital data converter in accordance with a predetermined data conversion algorithm the sampled input signal, after sampling in the tracking mode, to a digital signal; and 
 controlling the tracking mode of operation to initiate the sampling operation at a predetermined time prior to and dependent upon the initiation of the convert mode of operation, which predetermined time is not defined by the end of a prior convert mode of operation. 
 
   
   
     13. The method of  claim 12 , wherein the analog-to-digital data converter operates under the control of a data converter clock, wherein the convert mode operates over a predetermined number of clock cycles of the data converter clock. 
   
   
     14. The method of  claim 13 , wherein the step of controlling comprises controlling the operation of the analog-to-digital data converter in the tracking mode to sample the input signal for a predetermined amount of time after initiation thereof. 
   
   
     15. The method of  claim 14 , wherein the predetermined amount of time comprises a predetermined number of clock cycles of the data converter clock. 
   
   
     16. The method of  claim 15 , wherein the beginning of the tracking mode is controlled to operate in a plurality of different initiation modes controlled by external stimuli. 
   
   
     17. The method of  claim 16 , wherein one of the stimuli comprises the step of initiating the tracking mode in response to the setting of a data bit in a register which, when read in the set state, indicates the start of the tracking mode. 
   
   
     18. The method of  claim 17 , wherein the convert mode of operation is initiated at the end of the predetermined time such that setting of the data bit causes operation in the convert mode. 
   
   
     19. The method of  claim 16 , wherein one of the stimuli comprises the step of initiating the tracking mode in response to an elapse of time determined by a timer, the elapse of which indicates the start of the tracking mode. 
   
   
     20. The method of  claim 19 , wherein the convert mode of operation is initiated at the end of the predetermined time such that the elapse of time is the causative effect to initiate the convert mode of operation. 
   
   
     21. The method of  claim 12 , wherein the convert mode operates in accordance with a SAR data conversion algorithm.